Spinal fixation apparatus with enhanced axial support and methods for use

ABSTRACT

A spinal fixation system includes a plurality of anchor screw assemblies, e.g. including anchor screws and clamp assemblies defining rod passages therethrough. A rod is receivable in the rod passages between the anchor screw assemblies, and a spacer is securable on the rod. During use, a first anchor screw is screwed into a first vertebra, and a second anchor screw is screwed into a second vertebra adjacent the first vertebra, and clamp assemblies are mounted to each anchor screw. A rod is secured between the anchor screw assemblies, thereby fixing a relative spacing of the first and second vertebrae. A spacer is crimped onto the exposed portion of the rod between the anchor screw assemblies, the spacer extending between the anchor screw assemblies to prevent the anchor screw assemblies, and, consequently, the first and second vertebrae, from moving towards one another.

This application is a continuation-in-part of application Ser. No.09/861,278, filed May 17, 2001, the disclosure of which is expresslyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to apparatus and methods fortreating spinal disorders, and more particularly to spinal fixationsystems that may be secured between adjacent anchor screw assemblies,and methods for stabilizing, adjusting, or otherwise fixing adjacentvertebrae using such spinal fixation systems.

BACKGROUND

Various systems and methods have been suggested for treating spinaldisorders, such as degenerative discs, stenosis, trauma, scoliosis,kyphosis, or spondylolisthesis. For example, U.S. Pat. No. 5,545,166,naming the same inventor as the present application, discloses a spinalfixation system that includes a plurality of anchor screws, clampassemblies, pivot blocks, clamp blocks, and rods that are implantedalong a patient's spine to fix two or more adjacent vertebrae relativeto one another. The system generally includes a swing bolt anchor screw,a pivot block receivable on the swing bolt, and a clamp block receivinga rod therethrough that is pivotally attachable to the pivot block. Inaddition, the system includes one or more fixed anchor screws, and clampassemblies for receiving the rod therein. The clamp assemblies and pivotblock are receivable on the anchor screws by spindles that thread alonga threaded portion of the anchor screws.

During use, vertebrae to be treated are surgically exposed, and anarrangement of anchor screws and clamp accessories are selected. Forexample, a fixed anchor screw may be screwed into each of the vertebraeon either side of a first vertebra. A rod is selected that may extendbetween the fixed anchor screws and that may be bent to conform to theshape of the anatomy encountered. The rod is inserted through a looseclamp block, and the rod is placed in clamp assemblies that are receivedover the fixed anchor screws.

A swing bolt anchor screw is then screwed into the first vertebraadjacent the rod, and a pivot block is received on the swing bolt screw.The clamp block and/or pivot block are adjusted such that the clampblock may be engaged with a pivot on the pivot block. A set screw maythen be screwed into the clamp block to secure the clamp block to thepivot. A pair of set screws are also screwed into the clamp block tosecure the rod within the clamp block. Preferably, a pair of suchsystems are implanted on either side of the vertebrae.

During the procedure, it may be desirable to adjust the vertebraerelative to one another. Once the system(s) is(are) connected asdescribed above, the set screws may be loosened and the rod(s), clampblock(s), and/or pivot block(s) may be adjusted, e.g., by moving thespindle(s) to adjust the height of the pivot block(s) and/or clampassemblies on the anchor screws, by pivoting the swing bolt anchorscrew(s), and/or pivoting the clamp block(s) relative to the pivotblock(s). Once the vertebrae have been moved into a desired position,the set screws may be tightened, and the spindles secured in position bycrimping the walls surrounding the spindles.

An advantage of this system is that the swing bolt anchor screw, pivotblock, and clamp block arrangement allows the system to be adjustedabout two axes, i.e., the axis of the swing bolt anchor screw and theaxis of the pivot on the pivot block. However, because the system of the'166 patent is polyaxial, i.e., may pivot about multiple axes, there isgreater risk of the system coming out of alignment when the patientresumes normal physical activity.

This system is also very complicated, involving six parts, includingthree set screws, that are mounted on each swing bolt anchor screw. Inaddition, because the swing bolt is threaded, an intricate spindledevice is required in order to allow the pivot block and clampassemblies to be threaded onto the swing bolt, and still control theirorientation about the axis of the swing bolt. Thus, because of itscomplexity and many intricate parts, this system may be expensive tomanufacture and/or difficult to implant.

Accordingly, apparatus and methods for stabilizing, adjusting, and/orfixing vertebrae would be considered useful.

SUMMARY OF THE INVENTION

The present invention is directed to spinal fixation systems that may besecured between adjacent anchor screw assembles, e.g., to rods extendingbetween the anchor screw assemblies, and to methods for stabilizing,adjusting, or otherwise fixing adjacent vertebrae using such spinalfixation systems.

In accordance with one aspect of the present invention, a spinalfixation system is provided that includes a first anchor screw assemblyincluding a first passage and a first screw, the first screw having athreaded portion configured to be screwed into a first vertebra, and asecond anchor screw assembly including a second passage and a secondscrew, the second screw having a threaded portion configured to bescrewed into a second vertebra adjacent the first vertebra. In anexemplary embodiment, one or both of the anchor screw assemblies mayinclude a saddle or clamp assembly receivable on the respective screw,each saddle assembly including a rod passage therethrough defining thefirst and second passages. Preferably, the saddle assemblies includeupper and lower saddles or clamp portions that may together define therod passage.

A rod or other elongate member is receivable in the first and secondpassages, the elongate member including an exposed portion extendingbetween the first and second anchor screw assemblies. A spacer issecurable on the exposed portion of the elongate member, the spacerhaving a length substantially similar to a length of the exposed portionof the elongate member for preventing the first and second anchor screwassemblies from moving towards one another.

In accordance with another aspect of the present invention, a kit isprovided for stabilizing vertebrae relative to one another. Generally,the kit includes one or more substantially rigid rods, and a pluralityof “C” shaped spacers having a plurality of lengths, the spacersincluding opposing edges defining a pocket therebetween for receivingthe one or more rods therein. The kit may also include a plurality ofanchor screw assemblies, the anchor screw assemblies including anchorscrews and a plurality of clamp assemblies for receiving the one or morerods therein.

Optionally, the kit may also include a tool for crimping at least aportion of the opposing edges of the spacers around the one or more rodsto secure the spacers to the rods. In another option, the kit mayinclude an apparatus for bending the one or more rods, e.g., to conformsubstantially to a natural curvature of a patient's spinal column beingtreated.

In accordance with still another aspect of the present invention, amethod is provided for stabilizing vertebrae relative to one another,the vertebrae being disposed adjacent one another along a central spinalaxis. A first anchor screw may be screwed into a first vertebra, and asecond anchor screw may be screwed into a second vertebra adjacent thefirst vertebra. A rod or other elongate member may be secured betweenthe first and second anchor screws, e.g., using clamp assemblies,thereby fixing a relative distance of the first and second vertebrae.

A spacer, e.g., a “C” shaped clip, may be secured or otherwise placed onthe elongate member, e.g., by crimping the spacer around the elongatemember. Preferably, the spacer extends substantially an entire length ofthe elongate member that is exposed between the first and the secondanchor screws to prevent the first and second anchor from moving towardsone another. For example, the spacer may abut clamp assemblies on thefirst and second anchor screws, thereby preventing the clamp assemblies,and consequently the anchor screws, from moving substantially towardsone another. One or both of the clamp assemblies may have a tapered sideportion to enhance abutment of the spacer and the clamp assemblies ifthe elongate member is bent, e.g., to conform to the natural curvatureof the anatomy encountered.

In accordance with yet another aspect of the present invention, ananchor screw assembly is provided that includes a screw having a firstthreaded portion, and a second head portion. A swing bolt is pivotallycoupled to the second portion of the screw. The swing bolt defines afirst axis, and includes a noncircular region extending along the firstaxis, the noncircular region having a noncircular cross-section and asubstantially smooth wall. In addition, the swing bolt may include athreaded region on its end opposite the screw.

A clamp assembly may be provided that includes first and second clampportions that are receivable on the swing bolt. Each clamp portion has anoncircular first passage therethrough for receiving the noncircularregion of the swing bolt therethrough. Thus, the noncircular region andthe first passage have like cross-sections, thereby preventing rotationof the clamp assembly with respect to the swing bolt about the firstaxis when the noncircular region of the swing bolt is received in thefirst passages.

In addition, the first and second clamp portions have cooperatinggrooves therein, the cooperating grooves together defining a secondpassage extending along a second axis substantially transversely to thefirst axis when the first and second clamp portions are received on theswing bolt.

A fastener, e.g., a nut, is also provided for securing the clampassembly on the swing bolt, e.g., that may be threaded onto the threadedregion of the swing bolt to secure the clamp assembly on the swing bolt.In a preferred embodiment, the second portion of the screw includes ashoulder, and the clamp assembly may substantially engage the shoulderwhen the clamp assembly is fully secured on the swing bolt, therebypreventing the swing bolt from pivoting with respect to the screw.

In accordance with still another aspect of the present invention, aspinal fixation system is provided that includes a first anchor screwassembly, such as that described above. The first anchor screw assemblyincludes a first screw having a threaded portion, and a swing boltpivotally coupled to the screw and including a noncircular region. Thespinal fixation system also includes a plurality of clamp assemblies,including a first passage for receiving the first swing bolttherethrough, and a second passage for receiving an elongate member,e.g., a substantially rigid rod, therethrough. The dimensions of eachclamp assembly may be different, e.g., including a second passage thatis at one of a plurality of distances from the first passage and/or thatis oriented at a predetermined angle along the clamp assembly. Afastener may be used for securing a selected clamp assembly on the swingbolt. Thus, when the selected clamp assembly is received on the firstswing bolt, the first clamp assembly is fixed in a predeterminedorientation with respect to a first pivot axis of the first swing bolt.

The spinal fixation system also includes a second anchor screw assemblyincluding a second screw having a threaded portion and a hub, and asecond selected clamp assembly receivable on the hub. The second screwmay be a fixed screw or, preferably, a swing bolt anchor screw, similarto that described above. The second clamp assembly includes a thirdpassage therethrough along a third axis. The second screw assembly maybe oriented, when implanted, such that the third axis is substantiallytransverse to the first axis. Optionally, additional anchor screwassemblies may also be provided.

In accordance with another aspect of the present invention, a method isprovided for simple alignment or otherwise stabilizing vertebraerelative to one another using a plurality of swing bolt anchor screwassemblies, such as those described above. A threaded portion of a firstswing bolt anchor screw is screwed into a first vertebra until a firstpivot axis of the first swing bolt anchor screw is generally parallel tothe spinal axis. A threaded portion of a second swing bolt anchor screwis screwed into a second vertebra adjacent the first vertebra until asecond pivot axis of the second swing bolt anchor screw is substantiallytransverse to the first pivot axis. If desired, a third anchor screw (ormore) may be screwed into other vertebra adjacent to the first vertebra.

An angle of one or more swing bolts on the first and second swing boltanchor screws may be adjusted about the first and second pivot axes.Lower clamp portions may be placed on the swing bolts of the first andsecond swing bolt anchor screws, either before or after the angleadjustments described above. A rod may be placed on the lower clampportions, e.g., when the grooves in the lower clamp portions have beenproperly aligned with one another. Thus, the rod may extend between thefirst and second anchor screws, and between any additional anchor screwsadded generally in a straight line. In addition, if desired, the rod maybe bent, e.g., in a single plane, to a predetermined configuration basedupon anatomy encountered before securing the rod on the swing bolts.

Upper clamp portions may be secured on the swing bolts of the first andsecond swing bolt anchor screws, thereby securing the rod between theupper and lower clamp portions. For example, a nut or other fastener maybe threaded onto the swing bolt after the upper and lower clampportions, thereby securing the rod between the upper and lower clampportions and/or securing the clamp assemblies on the swing bolts. Thesefasteners may also be loosened to allow adjustment of the vertebraerelative to one another, and then the fasteners may again be tightenedto fix the vertebrae in desired relative positions. Optionally, aspacer, such as that described above, may be secured between the clampassemblies to prevent movement of the swing bolts towards one another.

Other objects and features of the present invention will become apparentfrom consideration of the following description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded side view of a spinal fixation system, inaccordance with the present invention.

FIG. 1B is a side view of the system of FIG. 1A implanted to stabilize aplurality of vertebrae.

FIG. 2A is a perspective view of a spacer clip, in accordance with thepresent invention.

FIG. 2B is a side view of a crimping tool for use with the spacer clipof FIG. 2A.

FIG. 3A is a perspective view of a preferred embodiment of an anchorscrew assembly, in accordance with the present invention.

FIG. 3B is an exploded perspective view of the anchor screw assembly ofFIG. 3A.

FIGS. 4A and 4B are perspective and side views, respectively, of a screwfor the anchor screw assembly of FIGS. 3A and 3B.

FIGS. 5A-5C are perspective and first and second side views,respectively, of a swing bolt for the anchor screw assembly of FIGS. 3Aand 3B.

FIGS. 6A-6C are perspective and first and second side views,respectively, of an assembled screw and swing bolt for the anchor screwassembly of FIGS. 3A and 3B.

FIGS. 7A-7C are perspective and first and second side views,respectively, of a first embodiment of a lower clamp portion for a clampassembly, in accordance with the present invention.

FIGS. 8A-8C are perspective and first and second side views,respectively, of a first embodiment of an upper clamp portion for aclamp assembly, in accordance with the present invention.

FIGS. 9A-9E are perspective views of alternative embodiments of a lowerclamp portion, in accordance with the present invention.

FIGS. 10A-10E are perspective views of alternative embodiments of anupper clamp portion, in accordance with the present invention.

FIGS. 11A and 11B are perspective and side views, respectively, ofanother embodiment of an anchor screw, in accordance with the presentinvention.

FIGS. 12A-12C show a spinal fixation system being implanted betweenvertebrae of a patient, in accordance with the present invention.

FIG. 13 shows a pair of spinal fixation systems implanted along apatient's spine, in accordance with the present invention.

FIG. 14 is a perspective view of another preferred embodiment of ananchor screw assembly, in accordance with the present invention.

FIGS. 15A and 15B are top and front views, respectively, of an upperclamp portion for use with the anchor screw assembly of FIG. 14.

FIG. 15C is a front view of an alternative embodiment of an upper clampportion for use with the anchor screw assembly of FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, FIGS. 1A and 1B show a preferred embodimentof a spinal fixation system 8, in accordance with the present invention.Generally, the system 8 includes a plurality of anchor screw assemblies,10, a rod 86 securable between the anchor screw assemblies 10, and oneor more spacer clips 90 securable to the rod 86. All of the componentsof the system 8 may be made from a variety of biocompatible materials,e.g., metals, and preferably from titanium or alloys including titanium.

The rod 86 may be a substantially rigid elongate member, e.g., a solidrod, having a generally round cross-section. Optionally, the rod 86 hasone or more flattened regions (not shown) extending between ends 88 ofthe rod 86. For example, the rod 86 may include opposing flattenedregions (not shown), thereby defining a flattened ellipticalcross-section. Optionally, the rod 86 may include serrations or teeth(not shown) extending between the ends 88, which may facilitate securingthe rod 86 to the anchor screw assemblies 10.

The rod 86 may be substantially straight initially (not shown), and maybe bent and/or curved during a procedure, e.g., to conform to thenatural curvature or lordosis of the anatomy encountered, as shown inFIG. 1A, and as described further below. The rod 86 is sufficientlyrigid, however, such that, once bent, the rod 86 may substantiallyretain its bent shape when subjected to forces experienced during normalactivity of a patient, as will be appreciated by those skilled in theart.

Turning to FIG. 2A, a spacer clip 90 is shown that may be secured to therod 86. Generally, the clip 90 is a “C” shaped member including opposingedges 91 defining a pocket 92 that extends between ends 94 of the clip90. The pocket 92 has a cross-section that is larger than the rod 86such that the clip 90 may be received at least partially around the rod86. The clip 90 may be malleable such that a tool, such as the crimpingtool 95 shown in FIG. 2B, may be used to crimp or otherwise compress atleast portions of the opposing edges 91 around the rod 86 after the clip90 has been placed on the rod 86 to secure the clip 90 to the rod 86.

A variety of clips may be provided, e.g., having standard lengths “L”and/or cross-sections. For example, a set of clips (not shown) may beprovided that have lengths from about one to about three centimeters(1-3 cm), e.g., at 0.125 centimeter intervals. The ends 94 of the clip90 are preferably substantially square, although alternatively, they maybe tapered, e.g., such that the length of the clip as measured along theedges 91 is greater than the length as measured from the bottom of thepocket 92 (not shown).

Turning to FIGS. 3-8, each of the anchor screw assemblies 10 includes ascrew 12, a swing bolt 14 pivotally coupled to the screw 12 to providean anchor screw 15, and a clamp assembly 16 securably received on theswing bolt 14, as shown in FIGS. 3A and 3B. Alternatively, other anchorscrew assemblies may be used to provide a system in accordance with thepresent invention. For example, a rigid anchor screw 90, such as thatshown in FIGS. 11A and 11B, may be used instead of an anchor screw 15including a swing bolt 14. In a further alternative, other anchor screwassemblies may be used, e.g., including saddle or clamp assembliesmounted on screw bolts, such as those disclosed in U.S. Pat. Nos.4,653,481, 5,487,744, and 5,545,166, the disclosures of which areexpressly incorporated herein by reference. Thus, any known anchor screwassemblies may be used, although the anchor screw assemblies shown anddescribed herein may be particularly advantageous.

Turning to FIGS. 4A and 4B, the screw 12 of the anchor screw 15generally includes a first threaded portion 20 terminating in a tip 22,and a second head portion 24 opposite the tip 22. The threaded portion20 may include a helical thread 21 defining a thread pattern, preferablyconfigured for substantially securing the screw 12 into bone, such as aportion of a vertebra (not shown). The thread spacing may be betweenabout three to six threads per centimeter (3-6 threads/cm), andpreferably about 4.8 threads per centimeter (about 12 threads per inch).The thread spacing may be substantially constant between the tip 22 andthe head portion 24 or may vary along the length of the threaded portion20.

The leading and trailing edges of axially adjacent portions of thethread 21 may define an inclusive angle “α” between them of betweenabout twenty to forty degrees (20-40°), and preferably about thirtydegrees (30°). Preferably, each thread 21 is rounded or tapers outwardlyfrom the root diameter to the major diameter of the thread 21, such thatthe leading and trailing edges on either side of a portion of the thread21 define tangent lines that intersect one another adjacent the outeredge of the respective portion of the thread 21. The thread 21 may havea height of between about 0.50-3.00 millimeters, and preferably betweenabout 0.60-2.00 millimeters.

The threaded portion 20 may have desired dimensions to accommodatethreading into bone, such as a vertebra (not shown). For example, thethreaded portion 20 may have an outer diameter between about 3.5-8.5millimeters, preferably between about 5.8-8.5 millimeters, and a lengthbetween about 25-65 millimeters, and preferably between about 35-65millimeters. The threaded portion 20 may have a substantially uniformmajor and minor diameter along its length. Alternatively, the threadedportion 20 may have a taper, e.g., reducing in minor and/or majordiameter from the head portion 24 towards the tip 22. The thread 21 mayhave a substantially uniform height, or may become increasingly higherfrom the head portion 24 towards the tip 22, e.g., if the threadedportion 20 is tapered, to provide a substantially uniform outer diameterfor the threaded portion 20.

In addition, the threaded portion 20 may include a pull-out portion 21A,which may facilitate manufacturing of the anchor screw 12 and/or mayimprove engagement of the screw 12 with bone into which the screw 12 isthreaded. Other thread patterns and screw designs may also be used foran anchor screw assembly in accordance with the present invention, asfound in U.S. Pat. Nos. 4,854,311, 5,034,011, and 5,226,766, thedisclosures of which are expressly incorporated herein by reference.

The head portion 24 generally has a cross-section larger than thethreaded portion 20 and includes a full-radius shoulder 28 opposite thethreaded portion 20. The shoulder 28 includes a predetermined radiusabout a pivot axis 35 to facilitate pivoting of the swing bolt 14 and/orthe clamp assembly 16 (shown in FIGS. 3A and 3B) with respect to thehead portion 24, as explained further below. The head portion 24includes a slot 30 therein extending generally parallel to alongitudinal axis 32 of the screw 12, thereby dividing the head portion24 into ears 26. Pin holes 34 extend through the ears 26 along the pivotaxis 35, i.e., substantially perpendicular to the longitudinal axis 32.

Turning to FIGS. 5A-5C, the swing bolt 14 includes an elongate body 34including a first looped region 36, a second noncircular intermediateregion 38, and a third threaded region 40 generally opposite the loopedregion 36. The looped region 36 may be substantially narrower than theother regions of the swing bolt 14, i.e., having a width slightlysmaller than a width of the slot 30 in the screw 12 such that the loopedregion 36 may be received in the slot 30 between the ears 26, as shownin FIGS. 6A-6C. The looped region 36 has a pin hole 37 therethrough thatextends substantially perpendicular to the longitudinal axis 32.

The noncircular region 38 of the swing bolt 14 is preferablysubstantially smooth-walled and has a noncircular cross-section,preferably for slidably receiving the clamp assembly 16 thereon (asshown in FIGS. 3A and 3B), while preventing rotation of the clampassembly 16 about longitudinal axis 33. In the preferred embodimentshown in FIGS. 5A-5C, one or more flat walls 42, and preferably twoopposing flat walls, are formed along the intermediate region 38. Thus,the cross-section may define a flattened elliptical shape, a “D” shape.Alternatively, other shapes may be used, such as a hexagon, a square, astar, or other noncircular geometric shape.

As shown in FIGS. 6A-6C, the looped region 36 of the swing bolt 14 maybe received in the slot 30 of the head portion 24, and a pin 44 may bereceived through the pin holes 34, 37 to provide anchor screw 15. Thepin 44 may fix the swing bolt 14 to the screw 12, while allowing theswing bolt 14 and screw 12 to pivot with respect to one another suchthat the longitudinal axes 32, 33 intersect, but define an angle “theta”greater than zero degrees, as shown in phantom in FIG. 6B.

Turning to FIGS. 7A-8C, the clamp assembly 16 (shown in FIGS. 3A and 3B)generally includes a first lower clamp portion 52 and a second upperclamp portion 72. The lower and upper clamp portions 52, 72 havenoncircular bolt passages 54, 74 that extend entirely through thembetween lower surfaces 56, 76 and upper surfaces 58, 78, respectively,thereby defining a first axis 60. The bolt passages 54, 74 preferablyhave a cross-section similar to the cross-section of the noncircularregion 42 of the swing bolt 14 (see FIGS. 3B, 5A, 5B, 6A, and 6B). Thus,the bolt passages 54, 74 may accommodate receiving the swing bolt 14therethrough, while preventing rotation of the clamp assembly 16 on theswing bolt 14, as explained further below.

In addition, the lower and upper clamp portions 52, 72 have generallysemi-cylindrical grooves 62, 82 therein that cooperate with one anotherwhen the clamp assembly 16 is assembled to define a rod passage 64, asshown in FIG. 3A. The rod passage 64 generally extends along a secondaxis 66 that is transverse to, and preferably substantiallyperpendicular to, the first axis 60. In the embodiment shown, the secondaxis 66 is also substantially perpendicular to a third axis 70 thatextends along a length of the lower clamp portion 52 substantiallyperpendicular to both the first and second axes 60, 66 (thus, the threeaxes 60, 66, 70 may be orthogonal to one another). The rod passage 64has a cross-section similar to a rod 86 (not shown, see FIG. 1A) thatmay be received therein. For example, the cross-section may be generallycircular, but optionally may be noncircular, e.g., circular with one ormore flattened walls, such as wall 83 shown in the upper clamp portion72 in FIGS. 8B and 8C. Alternatively, as shown in FIG. 3A, the rodpassage 64 may have other geometric shapes, similar to the bolt passages54, 74, described above. In a further alternative, one or both of thegrooves 62, 82 may include teeth or other serrations (not shown) forenhancing engagement with the rod received in the rod passage 64 (shownin FIG. 3A), either alone or in combination with one of thecross-sections described above. Exemplary serrations are shown in U.S.Pat. Nos. 4,653,481 and 5,545,164, the disclosures of which areexpressly incorporated herein by reference.

With particular reference to FIGS. 8A-8C, the groove 82 in the upperclamp portion 72 extends along the lower surface 76. The upper surface78 may be recessed around the bolt passage 74, thereby accommodating afastener (not shown) thereon, while minimizing the profile of theresulting clamp assembly. For example, the groove 82 may define a hump79 opposite the lower surface 76, which may be higher than the uppersurface 78. The hump 79 may have a height similar to a nut or otherfastener (not shown) that may be attached to a swing bolt (also notshown) that is inserted through the bolt passage 74. Thus, when afastener 18 (not shown, see FIG. 3A) engages the upper surface 78, theupper surface of the fastener 18 may define a height similar to the hump79 (also as shown in FIG. 3A), thereby substantially minimizing aprofile of the anchor screw assembly and/or reducing tissue irritation.

Returning to FIGS. 8A-8C, side edges 84 of the upper clamp portion maybe substantially square with the lower surface 76, i.e., the side edges84 may extend substantially parallel to the first axis 60.Alternatively, as shown in FIGS. 15A and 15B, the side edges 84′ may betapered. For example, the side edges 84′ of the upper clamp portion 72′may taper inwardly towards the hump 79′ such that they define an angle Δbetween about one and twenty degrees (1-20°) with the first axis 60′,and preferably about ten degrees (10°). Such a taper may be machinedinto the side edges 84′ or formed using other known methods.

Alternatively, as shown in FIG. 15C, instead of tapering the side edges84, the side edges 84 may be substantially square, and a spot face,recess, or notch 85″ may be formed around the groove 82,″ e.g., by spotfacing the side edges 84.″ These tapered or recessed features mayenhance abutment with ends 94 of the spacer clip 90 despite the naturalcurvature or lordosis of a spinal column (not shown) when the spacerclip 90 is secured to a curved rod 86 (not shown, see FIGS. 1A and 1B),as explained further below.

Turning to FIGS. 7A-7C, the groove 62 in the lower clamp portion 52extends along the upper surface 58. In addition, the lower clamp portion62 also includes a recess 68 in the lower surface 56 that intersects thebolt passage 54. The recess 68 preferably has a radius of curvaturesimilar to the shoulder 28 on the head portion 24 of the screw 12 (seeFIGS. 6A-6C), as explained further below.

Returning to FIGS. 3A, 3B, 7C, and 8C, the lower surface 76 of the upperclamp portion 72 and the upper surface 58 of the lower clamp portion 52are substantially flat such that the lower and upper clamp portions 52,72 may substantially abut one another to provide the rod passage 64.Alternatively, the upper and lower surfaces 58, 76 may include matingsegments, e.g., cooperating tabs and slots or other male/femaleconnectors (not shown), that may positively engage one another when thelower and upper clamp portions 52, 72 are disposed in the properorientation.

The clamp assembly 16 may be received on the swing bolt 14, e.g., byorienting the clamp assembly 16 such that the bolt passages 54, 74 areproperly aligned with the noncircular region of the swing bolt 14. Thelower clamp portion 52 may be directed over the swing bolt 14 and thenthe upper clamp portion 72 may be received over the swing bolt 14, i.e.,through the bolt passages 54, 74, respectively. A fastener, e.g., nut18, may be threaded onto the threaded region 40 of the swing bolt 14until it engages upper surface 78 of the upper clamp portion 72, therebyforcing the clamp assembly 16 towards the head portion 24 of the screw12. Consequently, the lower clamp portion 52 may abut the head portion24 such that the shoulder 28 is received in the recess 68 in the lowersurface 56.

Preferably, because of the mating shapes of the shoulder 28 and recess68, the lower clamp portion 52 may slide along the shoulder 28 as theswing bolt 14 is pivoted with respect to the screw 12. Once a desiredangle is obtained, the nut 18 may be further tightened until the wall ofthe recess 68 frictionally engages the shoulder 28, therebysubstantially securing the swing bolt 14 at the desired angle relativeto the screw 12.

Turning to FIGS. 9A-10E, several alternative embodiments of lower andupper clamp portions are shown that together may provide clampassemblies that may be received over the screw assembly 15 of FIGS.6A-6C. For example, the lower and upper clamp portions 152, 172 shown inFIGS. 9A and 10A are generally similar to that shown in FIGS. 7A and 8A,except that the flat regions 155, 175 of the bolt passages 154, 174 andthe recess 168 are offset ninety degrees from the previous embodiment.The resulting clamp assembly (not shown) may be mounted similar to theprevious embodiment, but offset ninety degrees with respect to theanchor screw (not shown).

Turning to FIGS. 9B and 10B, another set of lower and upper clampportions 252, 272 are shown that are similar to the embodiments of FIGS.9A and 10A, except that the grooves 262, 282 are located further awayfrom the bolt passages 254, 274 along the third axis 270. The resultingclamp assembly from these embodiments may be mounted on the anchor screwsimilar to the previous embodiment with the shoulder 28 of the screw 12being received in the recess 268. A rod (not shown) received in theresulting rod passage, however, will be disposed further from the anchorscrew than the previous embodiment.

Turning to FIGS. 9C and 10C, yet another set of lower and upper clampportions 352, 372 are shown that are similar to the embodiments of FIGS.9A and 10A, except that the bolt passages 354, 374 have an elongatedelliptical shape extending along the third axis 370. In addition, thelower surface 356 of the lower clamp portion 352 includes adjacentrecesses 368, 369 that intersect the bolt passage 354 and may overlapone another. The resulting clamp assembly from this embodiment may besecured to the anchor screw such that either of the recesses 368, 369slidably engages the shoulder of the screw (not shown), thereby allowinga rod (also not shown) received in the rod passage to be disposed at twopossible locations, e.g., distances, relative to the anchor screw.Optionally, more than two recesses (not shown) may be provided, therebyallowing the rod passage to be disposed at multiple distances from theanchor screw.

Turning to FIGS. 9D and 10D, still another set of lower and upper clampportions 452, 472 are shown that are similar to the embodiments of FIGS.7A and 8A, except that the grooves 462, 482 and recess 468 are alignedsuch that the second axis 466 defines an angle “β” with the third axis470. Preferably, the angle “β” is between about ten and seventy degrees(10-75°), and more preferably between about thirty and forty fivedegrees (30-45°). In addition, the flattened wall regions 455, 475 arealigned substantially parallel to the second axis 466, thereby alsodefining an angle “β” with respect to the third axis 470.

Turning to FIGS. 9E and 10E, another set of lower and upper clampportions 552, 572 are shown that are similar to the embodiments of FIGS.9D and 10D, except that the bolt passages 554, 574, recess 568, andgrooves 562, 582 are mirror opposites or opposite-hand of those in theprevious embodiment. Thus, it will be appreciated by those skilled inthe art that a variety of clamp assemblies may be providing including arange of dimensions, e.g., lengths, thicknesses, “β” angles, and thelike, in any combination or subcombination of the features describedabove.

Turning to FIGS. 11A and 11B, another preferred embodiment of an anchorscrew 90 is shown that includes a threaded portion 92 terminating in atip 93, and an enlarged head portion 94 including a noncircular region96 and a threaded region 98 opposite the tip 93. The threaded portion 92may include any of the features and/or dimensions described above forthe anchor screw 12 of FIGS. 4A-4C, e.g., thread pattern, outerdiameter, taper, and the like. The threaded region 98 may receive afastener, such as the nut described above (not shown), e.g., tosubstantially secure a clamp assembly (also not shown) on thenoncircular region 96, similar to the embodiment described above. Thus,the anchor screw 90 may receive any of the clamp assemblies describedabove.

To select a system 8, such as that shown in FIGS. 1A and 1B, a kit maybe provided (not shown). The kit may include a plurality of anchorscrews, clamp assemblies, and fasteners that may be selected based uponthe specific vertebrae being treated and/or based upon the anatomyencountered. Each anchor screw assembly may include an anchor screw,e.g., a pivoting or fixed anchor screw, and one or more clampassemblies. For example, a plurality of upper and lower clamp assembliesmay be provided, having different dimensions, as described above. Anappropriate pair, corresponding to the patient anatomy encountered, maybe selected for each anchor screw.

One or more rods may be provided, and an apparatus (not shown) may beprovided for bending the rod(s) in a desired configuration during aprocedure. Finally, a plurality of spacer clips may be provided, e.g.,having different lengths, as described above, and a tool, e.g., acrimper or plyers, may be provided for crimping the spacer clip. Thus, asystem in accordance with the present invention provides a modularitythat may easily accommodate a variety of anatomy and patients.

Turning to FIGS. 12A-12C and 13, an exemplary system 1000 is shown thatincludes a pair of rods 1002 that are each implanted along a spinalcolumn using three swing bolt anchor screws 1010-1014 and three clampassemblies, 1016-1020. Alternatively, one or more of the swing boltanchor screws, such as the outside anchor screws 1010, 1014, may bereplaced with nonpivoting anchor screws (such as that shown in FIGS. 11Aand 11B). In a further alternative, fewer or additional anchor screwsmay be implanted, e.g., to secure a shorter or longer rod and/or to fixfewer or additional vertebrae.

Preferably, the rods 1002 are implanted generally parallel to thecentral spinal axis on either side of the spinous processes 902, asshown in FIG. 13. The system 1000 may be used to provide adjustment ofthe vertebrae, e.g., to allow vertical or horizontal, medial or lateraladjustment. Although an implantation procedure for only one rod 1002 isdescribed below, it will be appreciated that a second rod (or evenadditional rods) may be implanted using a similar procedure.

Turning first to FIG. 12A, the vertebrae, e.g., vertebrae 910, 920, 930,to be stabilized are exposed, e.g., using conventional surgicalprocedures. The anchor screws 1010-1014 are screwed into the vertebrae910-930, respectively, e.g., into the pedicles. Preferably, the anchorscrews 1010-1014 are screwed in sufficiently to provide a predeterminedpivot axis with respect to a centerline spinal axis of the patient. Forexample, the anchor screw 1012 may be screwed into the pedicle until apivot axis 1032 of the anchor screw 1012 is disposed generally parallelto the centerline spinal axis 908. In contrast, the other anchor screws1010, 1014 may be screwed into their respective vertebrae until theirrespective pivot axes 1030, 1034 are disposed substantially transverseto the first pivot axis 1032, and preferably substantially perpendicularto the centerline spinal axis.

Clamp assemblies 1016-1020 are selected based upon the anatomyencountered. For example, the clamp assembly 1016 may be similar to theclamp assembly 52, 72 shown in FIGS. 7A and 8A, and the clamp assembly1018 may be similar to the clamp assembly 152, 172 of FIGS. 9A and 10A,i.e., having a longer length than the clamp assembly 1016. Finally, theclamp assembly 1020 may be similar to the clamp assembly 452, 472 shownin FIGS. 9B and 10B, i.e., having a groove 1028 a (see FIG. 12A) thatextends in line with the grooves 1024 a, 1026 a of the clamp assemblies1016, 1018.

The lower clamp portions 1016 a-1020 a of the clamp assemblies 1016-1020may be received over the noncircular regions (not shown) of the anchorscrews 1010-1014, as best seen in FIG. 12A.

A rod 1002 may be received in the grooves 1024 a-1028 a in the lowerclamp portions 1016 a-1020 a, thereby extending between the anchorscrews 1010-1014, as shown in FIG. 12B. If desired, the rod 1002 may bebent to a predetermined shape, as needed, to conform to the anatomyalignment encountered. Preferably, the rod 1002 is bent in only oneplane, e.g., the sagetal plane, while remaining substantially straightin the coronal plane, as shown in FIG. 1A. “Sagetal” plane, as usedherein, refers to the plane that may be seen from a lateral view of thepatient, e.g., that is viewed horizontally when the patient is lyingface-down (such as the plane seen in FIGS. 1A and 1B). “Coronal” planerefers to the plane that may be seen from an anterior or posterior viewof the patient, e.g., that is viewed vertically up the length of thespine when the patient is lying face-down (such as that shown in FIGS.12A-12C).

Optionally, if the rod 1002 includes one or more flattened regions 1004,the flattened region(s) 1004 may be oriented so that they may engagesimilar flattened regions (not shown) in the rod passages 1024-1028 inthe clamp assemblies 1016-1020 (e.g., in the upper clamp portions 1016b-1020 b).

One or more of the clamp assemblies 1016-1020 may be adjusted at anytime during the procedure. By adjusting the clamp assemblies 1016-1020,the swing bolts on the anchor screws 1010-1014 may be pivoted abouttheir respective pivot axes 1030-1034 with respect to the threadedportions that have been threaded into the vertebrae 910-930. Forexample, the lower clamp portions 1016 a-1020 a may be adjusted beforeand/or after the rod 1002 is received in the grooves 1024 a-1028 a.Because the pivot axes 1030-1034 of the swing bolt anchor screws1010-1014 are substantially transverse with respect to one another, auniaxial device (i.e., pivoting in a single axis) may be used to providemultiple degrees of freedom for moving the clamp assemblies 1016-1020relative to the rod 1002. This may minimize the amount of bendingrequired of the rod 1002, preferably requiring bending in only one plane(preferably, the sagetal plane), thereby substantially maximizing therigidity of the rod 1002.

As shown in FIG. 12C, upper clamp portions 1016 b-1020 b may be placedon the lower clamp portions 1016 a-1020 a, i.e., received on the swingbolts of the anchor screws 1010-1014. When properly placed, the grooves(not shown) in the upper clamp portions 1016 b-1020 b substantiallyengage the rod 1002. Fasteners, such as nuts 1022, may then by threadedonto the swing bolts, thereby substantially securing the rod 1002between the upper and lower clamp portions 1016-1020.

Preferably, the nuts 1022 are twelve point jam nuts. The nuts 1022 mayhave rounded upper edges, which may minimize tissue irritation, e.g., oftissue overlying the nuts 1022 after implantation of the system 1000. Inaddition, the nuts 1022 may include a crimpable rim (not shown), whichmay be crimped when the nuts are tightened to a desired torque, e.g., toprevent subsequent loosening of the nuts. Alternatively, hex nuts orother fasteners may be used.

Preferably, the lower clamp portions 1016 a-1020 a include radiusedrecesses (not shown) on their lower surfaces that intersect boltpassages for receiving the swing bolts 1010-1014 therein. These recessesmay slidably engage similarly radiused shoulders on screws of the swingbolts (not shown), as described above. Thus, as the angles of the swingbolts are adjusted, the shoulders may pivotally slide along the surfacesof the recesses of the lower clamp portions 1016 a-1020 a. Once adesired configuration is obtained, the nuts 1022 may be tightened,thereby causing the lower clamp portions 1016 a-1020 a to frictionallyengage the shoulders and secure the swing bolts with respect to thethreaded portions without substantially moving one or more of thevertebrae out of the desired position.

If it is desired to adjust the vertebrae 910-930 with respect to oneanother, the nuts 1022 may be loosened, and the vertebrae 910-930adjusted, thereby possibly changing the angle of one or more of theclamp assemblies 1016-1020 holding the rod 1002. Once a desiredarrangement is obtained, the nuts 1022 may be tightened, therebysecuring the clamp assemblies 1016-1020. Thus, with a system inaccordance with the present invention, each individual clamp assembly isuniaxial, i.e., may only be pivoted about a single axis. By setting theaxes of the anchor screws substantially transverse relative to oneanother, substantially flexibility may be obtained without substantiallycompromising vertebra position. Because of the uniaxial nature of theclamp assemblies, the system may be less likely to become misalignedwhen the patient resumes normal activity than a polyaxial system.

Once the final configuration of the clamp assemblies 1016-1020 and/oranchor screws 1010-1014 is determined, spacer clips 90 (not shown, seeFIGS. 1A and 1B) may be placed on the rod 1004 between adjacent anchorscrew assemblies.

For example, turning to FIGS. 1A and 1B, an exemplary system 8 is shownthat has been implanted into vertebrae 910, 920, 930. After vertebraldistraction or compression and before final tightening of the nuts 18,spacer clips 90 may be placed around and crimped to exposed portions ofrod 86 that extends between adjacent clamp assemblies 10, 10′.

In this exemplary system 8, two anchor screw assemblies 10 includingupper clamp portions 16 with square side edges 84 (such as that shown inFIG. 3A) and one anchor screw assembly 10′ (such as that shown in FIG.14) with an upper clamp portion 16′ with tapered side edges 84′ havebeen selected. Because of the natural curvature or lordosis defined bythe vertebrae 910, 920, 930, the longitudinal axes 33 of adjacent anchorscrews 15 may define an angle Δ relative to one another. To match thisnatural curvature, the rod 86 may be bent to also define an angle Δ.

The upper clamp portion 16′ may be tapered, as described above withreference to FIGS. 15A and 15B, also to define an angle Δ relative tothe longitudinal axis 33. With this anchor assembly 10′ selected, theopposing side edges 84, 84′ of the adjacent upper clamp portions 72, 72′may be oriented substantially parallel to one another, as best seen inFIG. 1B. The distance “L” between the opposing side edges 84, 84′ may bemeasured, and an appropriate spacer clip 90, e.g., having a lengthapproximately “L” (or less than “L”), i.e., corresponding substantiallyto the measured distance, may be placed on the exposed portion of therod 86 between the adjacent clamp assemblies 16, 16′.

The spacer clip 90 may be crimped around the rod 86, e.g., bycompressing the opposing edges 91 (not shown, see FIG. 2A) of the clip90 using a crimper tool 95 (not shown, see FIG. 2B) to malleably deformthe opposing edges 91 towards one another. The crimper tool 95 may besufficiently long that a substantial length of the clip 90 may beengaged therein. Alternatively, one or more successive portions alongthe length of the clip 90 may be crimped around the rod 86 with the tool95. This placement and crimping process may be repeated for each exposedportion of the rod(s) 90 extending between adjacent clamp assemblies 16,16′.

The spacer clips 90 provide axial support, e.g., once the patientreturns to a vertical position, thereby preventing the adjacent clampassemblies 16, 16′ from moving substantially towards one another. Thus,the spacer clips 90 may enhance the system 8 remaining in the finalconfiguration set during the procedure and minimize any slippage of thesystem 8 once the patient resumes normal activity.

In a further alternative, if the sides of the upper clamp portions arenot tapered, e.g., if the upper clamp portions include spotfaced angularrecesses around the rod grooves (not shown), the ends of the clip(s) maybe received in the recesses, thereby preventing the clip(s) from beingdislocated from the rod once the patient assumes normal activity. Forexample, the patient may be placed under traction or the vertebrae mayotherwise be distracted away from one another. This may providesufficient space between the adjacent clamp assemblies to allow thespacer clip(s) to be placed around and/or otherwise secured to therod(s). When distraction is removed, the vertebrae may return to adesired state, whereupon the spacer clip(s) substantially abut theadjacent clamp assemblies, thereby preventing axial movement of theclamp assemblies towards one another. In addition, the ends of theclip(s) may be received in the recesses in the sides of the clampassemblies, thereby further securing the clip(s) relative to the rod. Instill a further alternative, the spacer clips themselves may be tapered(not shown) to extend between and abut adjacent clamp assemblies.

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the appended claims.

I claim:
 1. A spinal fixation system, comprising: a first anchor screwassembly comprising a first passage and a first screw, the first screwhaving a threaded portion configured to be screwed into a firstvertebra; a second anchor screw assembly comprising a second passage anda second screw, the second screw having a threaded portion configured tobe screwed into a second vertebra adjacent the first vertebra; anelongate member receivable in the first and second passages forstabilizing the first and second vertebra with respect to each other,the elongate member comprising an exposed portion extending between thefirst and second anchor screw assemblies; and a “C” shaped spacersecurable to the exposed portion of the elongate member by compressingthe spacer onto the elongate member, the spacer having a lengthsubstantially similar to a length of the exposed portion of the elongatemember for preventing the first and second anchor screw assemblies frommoving substantially towards one another.
 2. A spinal fixation system,comprising: a first anchor screw assembly comprising a first passage anda first screw, the first screw having a threaded portion configured tobe screwed into a first vertebra, wherein the first anchor screwassembly comprises a first clamp assembly receivable on the first screwassembly, the first clamp assembly comprising the first passagetherethrough; a second anchor screw assembly comprising a second passageand a second screw, the second screw having a threaded portionconfigured to be screwed into a second vertebra adjacent the firstvertebra; an elongate member receivable in the first and second passagesfor stabilizing the first and second vertebra with respect to eachother, the elongate member comprising an exposed portion extendingbetween the first and second anchor screw assemblies; and a spacersecurable to the exposed portion of the elongate member, the spacerhaving a length substantially similar to a length of the exposed portionof the elongate member for preventing the first and second anchor screwassemblies from moving substantially towards one another.
 3. The spinalfixation system of claim 2, wherein the first clamp assembly comprisesupper and lower clamp portions defining the first passage therebetween.4. The spinal fixation system of claim 2, wherein the elongate member isat least partially curved, and wherein the first clamp assemblycomprises a tapered side edge defining an angle corresponding to anangle of curvature defined by the elongate member.
 5. A spinal fixationsystem, comprising: a first anchor screw assembly comprising a firstpassage and a first screw, the first screw having a threaded portionconfigured to be screwed into a first vertebra, wherein the first screwcomprises a head portion opposite the threaded portion comprising ashoulder, and wherein the first anchor screw assembly further comprisesa swing bolt pivotally coupled to a second portion of the screw and aclamp assembly on the swing bolt comprising the first passagetherethrough a second anchor screw assembly comprising a second passageand a second screw, the second screw having a threaded portionconfigured to be screwed into a second vertebra adjacent the firstvertebra; an elongate member receivable in the first and second passagesfor stabilizing the first and second vertebra with respect to eachother, the elongate member comprising an exposed portion extendingbetween the first and second anchor screw assemblies; and a spacersecurable to the exposed portion of the elongate member, the spacerhaving a length substantially similar to a length of the exposed portionof the elongate member for preventing the first and second anchor screwassemblies from moving substantially towards one another.
 6. The spinalfixation system of claim 5, wherein the swing bolt comprises anoncircular region, and wherein the clamp assembly comprises a passagehaving a noncircular cross-section similar to the noncircular region forseating the clamp assembly on the swing bolt.
 7. The spinal fixationsystem of claim 6, wherein the swing bolt comprises a threaded regionopposite the first screw, and wherein a fastener is threadable onto thethreaded region for securing the clamp assembly on the swing bolt.
 8. Aspinal fixation system, comprising: a first anchor screw assemblycomprising a first passage and a first screw, the first screw having athreaded portion configured to be screwed into a first vertebra; asecond anchor screw assembly comprising a second passage and a secondscrew, the second screw having a threaded portion configured to bescrewed into a second vertebra adjacent the first vertebra; an elongatemember receivable in the first and second passages for stabilizing thefirst and second vertebra with respect to each other, the elongatemember comprising an exposed portion extending between the first andsecond anchor screw assemblies; and a spacer securable to the exposedportion of the elongate member, the spacer having a length substantiallysimilar to a length of the exposed portion of the elongate member forpreventing the first and second anchor screw assemblies from movingsubstantially towards one another, wherein the spacer comprises a “C”shaped clip receivable around the elongate member, the clip comprisingopposing edges that may be compressed around the elongate member tosecure the clip to the elongate member.
 9. A spinal fixation system,comprising: a first anchor screw assembly comprising a first passage anda first screw, the first screw having a threaded portion configured tobe screwed into a first vertebra, wherein the first screw comprises ahead portion opposite the threaded portion comprising a shoulder, andwherein the first anchor screw assembly further comprises a swing boltpivotally coupled to a second portion of the screw, and a clamp assemblyon the swing bolt comprising the first passage therethrough, the clampassembly comprising first and second clamp portions, the first andsecond clamp portions having cooperating grooves therein togetherdefining the first passage when the first and second clamp portions arereceived on the swing bolt; a second anchor screw assembly comprising asecond passage and a second screw, the second screw having a threadedportion configured to be screwed into a second vertebra adjacent thefirst vertebra; an elongate member receivable in the first and secondpassages, the elongate member comprising an exposed portion extendingbetween the first and second anchor screw assemblies; and a spacersecurable to the exposed portion of the elongate member, the spacerhaving a length substantially similar to a length of the exposed portionof the elongate member for preventing the first and second anchor screwassemblies from moving substantially towards one another.
 10. The spinalfixation system of claim 9, wherein the shoulder is radiused, andwherein the first clamp portion comprises a recess adjacent a lowersurface of the first clamp portion that intersects the first passage,the recess having a radiused shape for pivotally receiving the shouldertherein before the clamp assembly is fully secured on the swing bolt.11. A method for stabilizing vertebrae of a patient relative to oneanother, the method comprising: screwing a first anchor screw assemblyinto a first vertebra; screwing a second anchor screw assembly into asecond vertebra adjacent the first vertebra; securing an elongate memberto the first and second anchor screws assemblies, thereby fixing arelative spacing of the first and second vertebrae; and securing a “C”shaped spacer to the elongate member, the spacer extending substantiallybetween the first and the second anchor screws to prevent the first andsecond anchor screws from moving towards one another after the patientreturns to an active vertical position.
 12. The method of claim 11,wherein the step of securing the spacer involves increasing a distancebetween the first and second vertebrae before securing the spacer to theelongate member.
 13. The method of claim 11, wherein the step ofsecuring the elongate member comprises: attaching a first clamp assemblyto the first anchor screw assembly; attaching a second clamp assembly tothe second anchor screw assembly; and securing the elongate member tothe first and second clamp assemblies.
 14. The method of claim 11,further comprising bending the elongate member to conform to a naturalcurvature of the vertebrae.
 15. The method of claim 11, furthercomprising: screwing a third anchor screw into a third vertebra adjacentthe first second vertebra; securing the elongate member to the thirdanchor screw; and securing a spacer to the elongate member between thesecond and the third anchor screws to prevent the second and thirdanchor from moving towards one another.
 16. A method for stabilizingvertebrae relative to one another, the method comprising: screwing afirst anchor screw into a first vertebra; screwing a second anchor screwinto a second vertebra adjacent the first vertebra; securing an elongatemember to the first and second anchor screws, thereby fixing a relativespacing of the first and second vertebrae; and securing a spacer to theelongate member, the spacer extending substantially between the firstand the second anchor screws to prevent the first and second anchor frommoving towards one another, and the spacer comprises a “C” shaped clip,and wherein the step securing a spacer comprises crimping the spaceraround at least a portion of the elongate member.
 17. A method forstabilizing vertebrae relative to one another, the method comprising:screwing a first anchor screw into a first vertebra; screwing a secondanchor screw into a second vertebra adjacent the first vertebra;securing an elongate member to the first and second anchor screws,thereby fixing a relative spacing of the first and second vertebrae; andsecuring a spacer to the elongate member, the spacer extendingsubstantially between the first and the second anchor screws to preventthe first and second anchor from moving towards one another, whereineach of the first and second anchor screws comprise a swing boltpivotally coupled to a threaded portion, the method comprising adjustingan angle of one or more of the swing bolts on the first and secondanchor screws about respective pivot axes to adjust alignment of thefirst and second anchor screws relative to one another.
 18. A kit forstabilizing vertebrae relative to one another, comprising: one or moresubstantially rigid rods for enabling the vertebrae to be stabilizedrelative one another, a plurality of “C” shaped spacers having aplurality of lengths, the spacers comprising opposing edges defining apocket therebetween for receiving the one or more rods therein; and aplurality of anchor screw assemblies, the anchor screw assembliescomprising anchor screws and a plurality of clamp assemblies forreceiving the one or more rods therein.
 19. The kit of claim 18, furthercomprising a crimping tool for crimping at least a portion of theopposing edges of the spacers around the one or more rods to secure thespacers to the rods.
 20. The kit of claim 18, further comprising anapparatus for bending the one or more rods to conform to a naturalcurvature of a patient's spinal column.
 21. The kit of claim 18, whereinthe plurality of clamp assemblies comprise a plurality of upper andlower clamp portions that may be mated together to define a passage forreceiving one of the one or more rods therein, the upper and lower clampportions comprising a plurality of lengths and passage configurations.